docs: def dvdot(s1, s2):
      """
      Compute the derivative of the dot product of two double
      precision position vectors.
  
      http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/dvdot_c.html
  
      :param s1: First state vector in the dot product.
      :type s1: 6-Element Array of floats
      :param s2: Second state vector in the dot product.
      :type s2: 6-Element Array of floats
      :return: The derivative of the dot product.
      :rtype: float
      """
      assert len(s1) is 6 and len(s2) is 6
      s1 = stypes.toDoubleVector(s1)
      s2 = stypes.toDoubleVector(s2)
      return libspice.dvdot_c(s1, s2)